March 31, 2005
09:00 AM (EST)

News Release Number: STScI-2005-11

Hubble Spies Cosmic Dust Bunnies

March 31, 2005: Like dust bunnies that lurk in corners and under beds, surprisingly
complex loops and blobs of cosmic dust lie hidden in the giant
elliptical galaxy NGC 1316. This image made from data obtained
with the NASA Hubble Space Telescope reveals the dust
lanes and star clusters of this giant galaxy that give evidence
that it was formed from a past merger of two gas-rich galaxies.

Q & A: Understanding the Discovery

1.
Why are scientists looking at Hubble images of NGC 1316?

Astronomers are using the ACS camera onboard Hubble to study star
clusters in several nearby giant elliptical galaxies. Globular
clusters are compact stellar systems with hundreds of thousands to
millions of stars formed at the same time. By counting the number
of globular clusters detected as a function of their brightness they
could, for the first time, see evidence of the gradual disruption of
star clusters created during a past merger of gas-rich galaxies.
The unprecedented sensitivity of the Hubble ACS data permitted the
team to detect faint globular clusters previously impossible to
reach.

2.
What are astronomers learning from this galaxy?

They found that the relative number of low-mass clusters is
significantly lower in the inner regions than in the outer regions, by
an amount consistent with theoretical predictions. The team's results
have improved our understanding of how elliptical galaxies and their
star clusters may have formed during galaxy mergers and then evolve to
resemble 'normal' elliptical galaxies after several billions of years.

3.
Where is this galaxy located?

NGC 1316 is on the outskirts of a nearby cluster of galaxies in the
southern constellation of Fornax, at a distance of about 75 million
light-years. It is one of the brightest ellipticals in the Fornax
galaxy cluster.

4.
When were these images taken?

These Hubble Advanced Camera for Surveys images were taken in March 2003.
The color composite is a combination of data taken in blue, yellow-green,
and infrared filters.

5.
Is this galaxy visible in other wavelengths or from the ground?

NGC 1316, also known as Fornax A, is one of the strongest and largest radio
sources in the sky, with radio lobes extending over several degrees of sky
(well off the Hubble image). Wide-field imagery from Cerro Tololo Interamerican
Observatory in Chile shows a bewildering variety of ripples, loops and plumes
immersed in the galaxy's outer envelope.